The adsorption of selected gases from a fluid stream provides a useful method of removing impurities from the fluid stream where the selected gases are impurities and a means to collect desired gases where the selected gas is useful in other processes. In one particular example, the selective adsorption of a gas from a fluid stream can be used to remove sulfur dioxide from an effluent gas stream such as the tower emissions from a coal-burning power plant. Selective adsorption can also be used to collect oxygen, lower alkenes, carbon monoxide, nitrogen oxides and other gases.
To be of any worthwhile economic value, it is highly critical that the adsorption be reversible, requiring minimal energy input. Compounds are known which reversibly adsorb gases from a fluid stream. For example, Cobalt (II), known as the Salen chelate and Fluomine chelate complexes of the Vaska type takeup oxygen reversibly. The adducts do not, under moderate conditions, release oxygen to regenerate the sorbent complex sufficiently readily to enable oxygen to be produced or nitrogen to be purified on a commercial scale.
McAuliffe et al U.S. Pat. No. 4,251,452 and continuation 4,323,543 disclose the use of manganese (II) complexes to reversibly adsorb oxygen, sulfur dioxide, hydrogen and ethylene. The manganese compounds disclosed have the following formula: EQU Mn(II)LX.sub.2
wherein L represents a mono-dentate ligand having the formula: ##STR1## in which formula R.sub.1, R.sub.2 and R.sub.3, which may be identical or different, represent substituted or unsubstituted alkyls, cycloalkyl or aryl groups or hydrogen, and X is a species capable of existing as an anion representing Cl.sup.-, Br.sup.-, I.sup.-, CN.sup.-, NO.sup.-.sub.2, NO.sup.-.sub.3, OH.sup.-, NCS.sup.- or NCO.sup.-. Because of the reactivity of the ligand towards water, it is necessary in the preparation and use of these manganese (II) complexes to maintain anhydrous conditions. The complexes react quickly with water and are irreversibly inactivated. For this reason, these compounds are totally useless in an ambient environment or under the rigorous conditions of a flue stack where high concentrations of moisture vapors may be encountered.
Many different manganese compounds have been reported. Various compounds formed from hydrated manganese and various nitrogen containing ligands are known. For example, in Vol. 35 of The Journal of the Indian Chemistry No. 10,1958 several different compounds formed from manganese chloride and ammonia are disclosed. The compounds formed and discussed in this article are formed in an alcohol solution which prevents formation of Mn(II) compounds. In Zhurnal Neorganicheskoi Khimii, 20, 1852-1856 (1975) there is disclosed compounds of manganese (II) thiocyanate reacted with aniline or a toluidine. Since the manganese compound is not anhydrous, the formed compound was not a Mn(II) compound.
The Jour. and Proc. Inst. Chem. Vol. 37, November, 1965 reports compounds formed from manganese chloride (dehydrated) and dilute solutions of amines in an alcohol solvent. The compounds are formed in dry air. Oxygen present during the formation prevents formation of an Mn(II) compound. These references do not teach any method of adsorbing gas. Further none of these reported compounds adsorb oxygen or any other gases.